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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

428

FOOT OIL

alcohols, hydrocarbons, etc.) ;   hydroxy-acids, up to 2%
50% ;   saponification number, 185-195 ;   titer, 36-42°.

acidity, not above

FOOT   OIL

This is obtained more especially from the feet of the ox, but also from
those of the sheep and horse. It is a pale yellow, almost odourless liquid,
solidifying only below o° (at about —5°). Its characters are indicated in
Table XLVII.

Detection of Adulterations.—The oil may be adulterated with mineral,
vegetable or marine animal oils, these additions being detectable by deter-
mining the various characters of the oil. Mineral oils lower the specific
gravity and the saponification and iodine numbers and may be identified
by investigation of the unsaponifiable substances (see General Methods, 19).
Vegetable oils give Bellier's reaction and the other general reactions of
seed oils (see General Methods, 23). By means of the special reactions and
tests, colza, cottonseed and sesame oils (q.v.) may be identified. Pure
foot oil gives no colour reaction and does not contain; arachidic and lignoceric
acids or erucic acid. The presence of phytosterol would serve to confirm
adulteration with vegetable seed oil (see Hog's Fat). Marine animal oils
raise the specific gravity and the iodine number and may be identified by
the special reactions indicated in the article on fish oils, etc.

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* *

For use as lubricants, foot oil should remain liquid and clear at o° for a
long time, should not contain more than 2% of free acids calculated as oleic
acid, and should not contain extraneous oils. A drop lying in a thin film on
a glass plate and kept at 50° for 24 hours should not resinify or dry up but
should be easily removable from the glass.

Fish and other Marine Animal Oils

These oils may be divided into three classes : (i) Fish oils proper,
obtained from herrings, sardines, pilchards, sprats, tunny fish, shad, or
from the residues obtained in the preparation of these fish; (2) Blubber
oils (train oils), from the marine mammifers, the seal and whale; and (3)
Liver oils, mainly from cod-liver but to a smaU extent from the liver of the
ray, skate, etc.

Fish and blubber oils and cod-liver oil are treated separately in the two
following articles; here, however, we shall give certain special reactions
which are common to the three classes of oil and serve to distinguish all these
oils from other fatty substances, either animal or vegetable.

Characteristic Reactions.—These reactions, which are now known
to be trustworthy, are the following:

(a) REACTION OF THE OCTABROMO-COMPOUNDS (given by Halphen, and
modified by Lewkowitsch, Marcusson and Huber) : From about 20 c.c.
of^the oil the fatty acids are extracted in the usual manner, 10 c.c. of the
acids being then shaken vigorously, in a cylinder with a ground stopper,od products is 36-44°, the acidity may exceed 50%,